160:, a potential difference can be created between the illuminated and non-illuminated faces of a semiconductor slab. Generally this potential is created through the depth of the slab, whether it is a bulk semiconductor or a polycrystalline film. The difference between these cases is that in the latter, a photovoltage can be created in each one of the microcrystallites. As was mentioned above, in the oblique deposition process inclined crystallites are formed in which one face can absorb light more than the other. This may cause a photovoltage to be generated along the film, as well as through its depth. The transfer of
294:
134:, held at an angle with respect to the direction of the incident vapor. However, the photovoltage was found to be very sensitive to the conditions and procedure at which the samples were prepared. This made it difficult to get reproducible results which is probably the reason why no satisfactory model for it has been accepted thus far. Several models were, however, suggested to account for the extraordinary phenomenon and they are briefly outlined below.
330:, i.e. electrons are moving towards higher fermi level or holes are moving towards lower fermi level. This is unusual: For example, in a normal silicon solar cell, electrons move in the direction of decreasing electron-quasi-fermi level, and holes move in the direction of increasing hole-quasi-fermi-level, consistent with the
305:. The blue arrows indicate radiative transitions, i.e. an electron can absorb a UV photon to go from A to B, or it can emit a UV photon to go from B to A. The purple arrows indicate nonradiative transitions, i.e. an electron can go from B to C by emitting many phonons, or can go from C to B by absorbing many phonons.
353:
one or two unit cells or mean-free-paths (this displacement is sometimes called the "anisotropy distance"). This is required because if an electron is excited into a mobile, delocalized state, and then it scatters a few times, then its direction is now randomized and it will naturally start following
242:
pairs are generated and cause a compensation of the charge in the surface and within the crystallites. If it is assumed that the optical absorption depth is much less than the space charge region in the crystallites, then, because of their inclined shape more light is absorbed in one side than in the
164:
at the surface of crystallites is assumed to be hindered by the presence of some unspecified layer with different properties, thus cancellation of consecutive Dember voltages is being prevented. To explain the polarity of the PV which is independent of the illumination direction one must assume that
308:
When light is shining, an electron in response to the time-varying electric field of light will occasionally move right by absorbing a photon and going from A to B to C. However, it will almost never move in the reverse direction, C to B to A, because the transition from C to B cannot be excited by
141:
in the films. Among the first attempts to explain the APE were few that treated the film as a single entity, such as considering the variation of sample thickness along its length or a non-uniform distribution of electron traps. However, studies that followed generally supported models that explain
341:
This also explains why large open-circuit voltages tend to be seen only in crystals that (in the dark) have very low conductivity: Any electrons that can freely move through the crystal (i.e., not requiring photons to move) will follow the drift-diffusion equation, which means that these electrons
361:
For example, it might be the case that when an electron absorbs a photon, it is disproportionately likely to wind up in a state where it is moving leftward. And perhaps each time a photon excites an electron, the electron moves leftward a bit and then immediately relaxes into ("gets stuck in") an
370:
quickly relax back to an immobile state, but instead keeps moving around the crystal and scattering randomly, then the electron will eventually "forget" that it was moving left, and it will wind up being pulled rightward by the electric field. Again, the total leftward motion of an electron, per
193:
layer at the interface between the two structures. A potential barrier is formed due to a combination of the band gap difference and the electric fields produced at the interface. One should remember that this model can be invoked to explain anomalous PV effect only in those materials that can
374:
A consequence is that the quantum efficiency of a thick device is extremely low. It may require millions of photons to bring a single electron from one electrode to the other. As the thickness increases, the current goes down as much as the voltage goes up.
43:
Although the voltage is unusually high, the short-circuit current is unusually low. Overall, materials that exhibit the anomalous photovoltaic effect have very low power generation efficiencies, and are never used in practical power-generation systems.
76:, and occurs because of non-centrosymmetry. Specifically, the electron processesâphoto-excitation, scattering, and relaxationâoccur with different probabilities for electron motion in one direction versus the opposite direction.
125:
silicon systems. Observed photovoltages were found to reach hundreds, and in some cases even thousands of volts. The films in which this effect was observed were generally thin semiconducting films that were deposited by vacuum
321:
There are several aspects of the bulk photovoltaic effect that distinguish it from other kinds of effects: In the power-generating region of the I-V curve (between open-circuit and short-circuit), electrons are moving in the
259:, and occurs because of non-centrosymmetry. The electron processes like photo-excitation, scattering, and relaxation may occur with different probabilities for electrons moving one direction versus the opposite direction.
312:
Because the electrons undergo a "shift" each time they absorb a photon (on average), this dc photocurrent with amplitude proportional to the square of the applied field is sometimes called a "shift current".
61:
materials can develop stripes consisting of parallel ferroelectric domains, where each domain acts like a photovoltaic and each domain wall acts like a contact connecting the adjacent
301:
Shown at right is an example of a simple system that would exhibit the bulk photovoltaic effect. There are two electronic levels per unit cell, separated by a large energy gap, say 3
142:
the effect as resulting from a series of microelements contributing additively to the net photovoltage. The more popular models used to explain the photovoltage are reviewed below.
243:
other. Thus a difference in the reduction of the charge is created between the two sides. This way a photovoltage parallel to the surface is developed in each crystallite.
593:
32:
and insulators. The "anomalous" refers to those cases where the photovoltage (i.e., the open-circuit voltage caused by the light) is larger than the
378:
In some cases, the current has a different sign depending on the light polarization. This would not occur in an ordinary solar cell like silicon.
349:
Each time one electron absorbs one photon (in the power-generating region of the I-V curve), the resulting electron displacement is, on average,
338:
because the quasi-fermi-levels are split. A bulk photovoltaic, by contrast, can generate power without any splitting of quasi-fermi-levels.
166:
916:
A. M. Glass; D. von der Linde; T. J. Negran (1974). "Highâvoltage bulk photovoltaic effect and the photorefractive process in LiNbO3".
707:
Reuter
Herbert, Schmitt Heinz (1995). "Anomalous photovoltaic effect and negative photoconductivity in thin, amorphous GaAsâSi films".
654:
Pal, U.; Saha, S.; Chaudhuri, A. K.; Banerjee, H. (1991). "The anomalous photovoltaic effect in polycrystalline zinc telluride films".
212:
through the microcrystallites, with an orientation such as to give a non-zero total photovoltage. This is equivalent to an array of
362:
immobile stateâuntil it absorbs another photon and the cycle repeats. In this situation, a leftward electron current is possible
742:
Levi
Aharoni, Hadar; Azulay, Doron; Millo, Oded; Balberg, Isaac (2008). "Anomalous photovoltaic effect in nanocrystalline Si/SiO
644:
H. Kallmann, B. Kramer, E. Haidenmanakis, W. J. McAleer, H. Barkemeyer, and P. I. Pollak, J. Electrochem. Soc. 108, 247 (1961).
238:
region in the crystallites, in case that the crystallites are small enough. Under illumination of the inclined crystallites
208:
It was suggested by
Starkiewicz that the anomalous PV is developed due to a distribution gradient of positive and negative
309:
photons, but instead requires an improbably large thermal fluctuation. Therefore, there is a net rightward photocurrent.
51:
1111:
366:
an electric field pushing electrons in the opposite direction. However, when a photon excites an electron, it does
282:
54:, so that the overall open-circuit voltage across the sample is large, potentially much larger than the bandgap.
331:
327:
186:
127:
1106:
354:
the drift-diffusion equation. However, in the bulk photovoltaic effect, the desired net electron motion is
387:
995:
1065:
Ralph von Baltz & Wolfgang Kraut (1981). "Theory of the bulk photovoltaic effect in pure crystals".
587:
297:
An example of a simple system that would exhibit the bulk photovoltaic effect. See text for description.
114:
285:
or other methods can predict the extent to which a material will exhibit the bulk photovoltaic effect.
90:
50:
First, in polycrystalline materials, each microscopic grain can act as a photovoltaic. Then the grains
861:
S. M. Ryvkin, Photoelectric
Effects in Semiconductors, page 296, (Consultants Bureau, New York, 1964).
1074:
1020:
965:
925:
887:
810:
755:
716:
663:
616:
557:
507:
449:
225:
182:
956:
W.T.H. Koch; R. Munser; W. Ruppel; P. WĂźrfel (October 1975). "Bulk photovoltaic effect in BaTiO3".
408:
293:
209:
151:
131:
25:
65:(or vice versa). Again, domains add in series, so that the overall open-circuit voltage is large.
1044:
1010:
826:
575:
523:
473:
1036:
771:
465:
157:
118:
98:
230:
The interface between crystallites may contain traps for charge carriers. This may lead to a
1082:
1028:
973:
933:
895:
818:
763:
724:
671:
624:
565:
515:
457:
433:
S.Y. Yang; J. Seidel; S.J. Byrnes; P. Shafer; C.-H. Yang; M.D. Rossell; et al. (2010).
413:
391:
271:
263:
122:
94:
996:"First Principles Calculation of the Shift Current Photovoltaic Effect in Ferroelectrics"
788:
J. I. Pankove, Optical
Processes in Semiconductors, (Dover Publications, New York, 1975).
1078:
1024:
969:
929:
891:
814:
759:
720:
667:
620:
561:
511:
453:
688:
M. D. Uspenskii, N. G. Ivanova, and I. E. Malkis, Sov. Phys.- Semicond. 1, 1059 (1968).
403:
252:
231:
161:
69:
872:
216:. However, the mechanism by which such p-n junctions may be formed was not explained.
1100:
977:
830:
822:
302:
239:
62:
58:
37:
29:
1048:
899:
527:
477:
1032:
579:
235:
213:
203:
178:
498:
V.M. Fridkin (2001). "Bulk photovoltaic effect in noncentrosymmetric crystals".
801:
Johnson H R (1975). "The anomalous photovoltaic effect in cadmium telluride".
1086:
775:
169:
rates at opposite faces of a crystallite, which is a weakness of this model.
434:
138:
106:
1040:
469:
461:
93:
et al. in 1946 on PbS films and was later observed on other semiconducting
546:"Photovoltaic Effects Exhibited in High-resistance Semi-conducting Films"
33:
852:
G. Brincourt and S. Martinuzzi, C. R. Acad. Sci. Paris 266, 1283 (1968).
262:
This effect was first discovered in the 1960s. It has been observed in
102:
937:
767:
697:
E. I. Adirovich and L. M. Gol'Dshtein, Sov. Phys. Dokl. 9, 795 (1965).
628:
607:
Goldstein, B.; Pensak, L. (1959). "HighâVoltage
Photovoltaic Effect".
519:
728:
675:
570:
545:
190:
843:
V. M. Lyubin and G. A. Fedorova, Sov. Phys. Dokl. 135, 1343 (1960).
1015:
292:
255:
can develop a giant photovoltage. This is specifically called the
72:
can develop a giant photovoltage. This is specifically called the
873:"The photogalvanic effect in media lacking a center of symmetry"
435:"Above-bandgap voltages from ferroelectric photovoltaic devices"
371:
photon absorbed, cannot be much larger than the mean free path.
247:
Bulk photovoltaic effect in a non-centrosymmetric single crystal
110:
386:
The bulk photovoltaic effect is believed to play a role in the
189:
structures, an asymmetric barrier can be formed by a residual
40:. In some cases, the voltage may reach thousands of volts.
346:
from the photocurrent and reduce the photovoltaic effect.
358:
the direction predicted by the drift-diffusion equation.
156:
When photogenerated electrons and holes have different
137:
The oblique deposition can lead to several structure
47:
There are several situations in which APE can arise.
544:Starkiewicz J., Sosnowski L., Simpson O. (1946).
1060:
1058:
539:
537:
493:
491:
489:
487:
8:
989:
987:
911:
909:
592:: CS1 maint: multiple names: authors list (
194:demonstrate two types of crystal structure.
951:
949:
947:
796:
794:
640:
638:
1014:
569:
177:This model suggests that when a material
425:
68:Third, a perfect single crystal with a
994:S. M. Young & A. M. Rappe (2012).
585:
871:V.I. Belincher; B.I. Sturman (1980).
803:Journal of Physics D: Applied Physics
80:Series-sum of grains in a polycrystal
57:Second, in a similar manner, certain
7:
165:there exists a large difference in
14:
251:A perfect single crystal with a
900:10.1070/PU1980v023n03ABEH004703
334:. Power generation is possible
326:that you would expect from the
281:Theoretical calculations using
1033:10.1103/PhysRevLett.109.116601
220:The surface photovoltage model
173:The structure transition model
89:This effect was discovered by
1:
253:non-centrosymmetric structure
70:non-centrosymmetric structure
18:anomalous photovoltaic effect
978:10.1016/0038-1098(75)90735-8
278:) and many other materials.
1128:
958:Solid State Communications
823:10.1088/0022-3727/8/13/015
709:Journal of Applied Physics
656:Journal of Applied Physics
609:Journal of Applied Physics
223:
201:
149:
283:density functional theory
130:onto a heated insulating
1087:10.1103/PhysRevB.23.5590
332:drift-diffusion equation
328:drift-diffusion equation
257:bulk photovoltaic effect
74:bulk photovoltaic effect
28:which occurs in certain
1003:Physical Review Letters
918:Applied Physics Letters
748:Applied Physics Letters
500:Crystallography Reports
317:Distinguishing features
146:The PhotoâDember effect
462:10.1038/nnano.2009.451
388:photorefractive effect
298:
198:The p-n junction model
442:Nature Nanotechnology
296:
36:of the corresponding
226:surface photovoltage
1079:1981PhRvB..23.5590V
1025:2012PhRvL.109k6601Y
970:1975SSCom..17..847K
930:1974ApPhL..25..233G
892:1980SvPhU..23..199B
815:1975JPhD....8.1530J
760:2008ApPhL..92k2109L
721:1995JAP....77.3209R
668:1991JAP....69.6547P
621:1959JAP....30..155G
562:1946Natur.158...28S
512:2001CryRp..46..654F
454:2010NatNa...5..143Y
409:Photovoltaic effect
152:Photo-Dember effect
26:photovoltaic effect
324:opposite direction
299:
1112:Energy conversion
1073:(10): 5590â5596.
1067:Physical Review B
938:10.1063/1.1655453
809:(13): 1530â1541.
768:10.1063/1.2897294
629:10.1063/1.1735125
520:10.1134/1.1387133
119:amorphous silicon
24:) is a type of a
1119:
1091:
1090:
1062:
1053:
1052:
1018:
1000:
991:
982:
981:
953:
942:
941:
913:
904:
903:
877:
868:
862:
859:
853:
850:
844:
841:
835:
834:
798:
789:
786:
780:
779:
739:
733:
732:
729:10.1063/1.358674
715:(7): 3209â3218.
704:
698:
695:
689:
686:
680:
679:
676:10.1063/1.348865
662:(9): 6547â6555.
651:
645:
642:
633:
632:
604:
598:
597:
591:
583:
573:
571:10.1038/158028a0
541:
532:
531:
495:
482:
481:
439:
430:
414:Virtual particle
234:and an opposite
117:, as well as on
97:films including
1127:
1126:
1122:
1121:
1120:
1118:
1117:
1116:
1097:
1096:
1095:
1094:
1064:
1063:
1056:
998:
993:
992:
985:
955:
954:
945:
915:
914:
907:
875:
870:
869:
865:
860:
856:
851:
847:
842:
838:
800:
799:
792:
787:
783:
745:
741:
740:
736:
706:
705:
701:
696:
692:
687:
683:
653:
652:
648:
643:
636:
606:
605:
601:
584:
543:
542:
535:
497:
496:
485:
437:
432:
431:
427:
422:
400:
392:lithium niobate
384:
319:
291:
277:
272:barium titanate
269:
264:lithium niobate
249:
228:
222:
206:
200:
175:
154:
148:
123:nanocrystalline
95:polycrystalline
87:
82:
12:
11:
5:
1125:
1123:
1115:
1114:
1109:
1107:Semiconductors
1099:
1098:
1093:
1092:
1054:
1009:(11): 116601.
983:
964:(7): 847â850.
943:
905:
880:Sov. Phys. Usp
863:
854:
845:
836:
790:
781:
754:(11): 112109.
743:
734:
699:
690:
681:
646:
634:
615:(2): 155â161.
599:
533:
506:(4): 654â658.
483:
424:
423:
421:
418:
417:
416:
411:
406:
404:Semiconductors
399:
396:
383:
380:
318:
315:
290:
289:Simple example
287:
275:
267:
248:
245:
232:surface charge
224:Main article:
221:
218:
202:Main article:
199:
196:
174:
171:
150:Main article:
147:
144:
121:films and in
86:
83:
81:
78:
30:semiconductors
13:
10:
9:
6:
4:
3:
2:
1124:
1113:
1110:
1108:
1105:
1104:
1102:
1088:
1084:
1080:
1076:
1072:
1068:
1061:
1059:
1055:
1050:
1046:
1042:
1038:
1034:
1030:
1026:
1022:
1017:
1012:
1008:
1004:
997:
990:
988:
984:
979:
975:
971:
967:
963:
959:
952:
950:
948:
944:
939:
935:
931:
927:
923:
919:
912:
910:
906:
901:
897:
893:
889:
885:
881:
874:
867:
864:
858:
855:
849:
846:
840:
837:
832:
828:
824:
820:
816:
812:
808:
804:
797:
795:
791:
785:
782:
777:
773:
769:
765:
761:
757:
753:
749:
746:composites".
738:
735:
730:
726:
722:
718:
714:
710:
703:
700:
694:
691:
685:
682:
677:
673:
669:
665:
661:
657:
650:
647:
641:
639:
635:
630:
626:
622:
618:
614:
610:
603:
600:
595:
589:
581:
577:
572:
567:
563:
559:
555:
551:
547:
540:
538:
534:
529:
525:
521:
517:
513:
509:
505:
501:
494:
492:
490:
488:
484:
479:
475:
471:
467:
463:
459:
455:
451:
447:
443:
436:
429:
426:
419:
415:
412:
410:
407:
405:
402:
401:
397:
395:
393:
389:
381:
379:
376:
372:
369:
365:
359:
357:
352:
347:
345:
339:
337:
333:
329:
325:
316:
314:
310:
306:
304:
295:
288:
286:
284:
279:
273:
265:
260:
258:
254:
246:
244:
241:
240:electron-hole
237:
233:
227:
219:
217:
215:
214:p-n junctions
211:
210:impurity ions
205:
197:
195:
192:
188:
184:
180:
172:
170:
168:
167:recombination
163:
159:
153:
145:
143:
140:
135:
133:
129:
124:
120:
116:
112:
108:
104:
100:
96:
92:
84:
79:
77:
75:
71:
66:
64:
63:photovoltaics
60:
59:ferroelectric
55:
53:
52:add in series
48:
45:
41:
39:
38:semiconductor
35:
31:
27:
23:
19:
1070:
1066:
1006:
1002:
961:
957:
921:
917:
883:
879:
866:
857:
848:
839:
806:
802:
784:
751:
747:
737:
712:
708:
702:
693:
684:
659:
655:
649:
612:
608:
602:
588:cite journal
556:(4001): 28.
553:
549:
503:
499:
448:(2): 143â7.
445:
441:
428:
385:
382:Applications
377:
373:
367:
363:
360:
355:
350:
348:
343:
340:
335:
323:
320:
311:
307:
300:
280:
261:
256:
250:
236:space charge
229:
207:
204:p-n junction
179:crystallizes
176:
155:
136:
88:
73:
67:
56:
49:
46:
42:
21:
17:
15:
139:asymmetries
128:evaporation
91:Starkiewicz
1101:Categories
924:(4): 233.
886:(3): 199.
420:References
158:mobilities
1016:1202.3168
831:250772486
776:0003-6951
187:hexagonal
132:substrate
107:Germanium
1049:13710483
1041:23005660
528:98554369
478:16970573
470:20062051
398:See also
356:opposite
344:subtract
181:both in
162:carriers
34:band gap
1075:Bibcode
1021:Bibcode
966:Bibcode
926:Bibcode
888:Bibcode
811:Bibcode
756:Bibcode
717:Bibcode
664:Bibcode
617:Bibcode
580:4109726
558:Bibcode
508:Bibcode
450:Bibcode
364:despite
351:at most
103:Silicon
85:History
1047:
1039:
829:
774:
578:
550:Nature
526:
476:
468:
274:(BaTiO
266:(LiNbO
191:dipole
1045:S2CID
1011:arXiv
999:(PDF)
876:(PDF)
827:S2CID
576:S2CID
524:S2CID
474:S2CID
438:(PDF)
342:will
183:cubic
1037:PMID
772:ISSN
594:link
466:PMID
336:only
185:and
113:and
111:ZnTe
99:CdTe
16:The
1083:doi
1029:doi
1007:109
974:doi
934:doi
896:doi
819:doi
764:doi
725:doi
672:doi
625:doi
566:doi
554:158
516:doi
458:doi
390:in
368:not
270:),
115:InP
22:APE
1103::
1081:.
1071:23
1069:.
1057:^
1043:.
1035:.
1027:.
1019:.
1005:.
1001:.
986:^
972:.
962:17
960:.
946:^
932:.
922:25
920:.
908:^
894:.
884:23
882:.
878:.
825:.
817:.
805:.
793:^
770:.
762:.
752:92
750:.
723:.
713:77
711:.
670:.
660:69
658:.
637:^
623:.
613:30
611:.
590:}}
586:{{
574:.
564:.
552:.
548:.
536:^
522:.
514:.
504:46
502:.
486:^
472:.
464:.
456:.
444:.
440:.
394:.
303:eV
109:,
105:,
101:,
1089:.
1085::
1077::
1051:.
1031::
1023::
1013::
980:.
976::
968::
940:.
936::
928::
902:.
898::
890::
833:.
821::
813::
807:8
778:.
766::
758::
744:2
731:.
727::
719::
678:.
674::
666::
631:.
627::
619::
596:)
582:.
568::
560::
530:.
518::
510::
480:.
460::
452::
446:5
276:3
268:3
20:(
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.