Ž . Journal of Non-Crystalline Solids 227–230 1998 1291–1294 Photocarrier collection in a-SiC:Hrc-Si heterojunction solar cells M.W.M. van Cleef a, ) , F.A. Rubinelli a , J.K. Rath a , R.E.I. Schropp a , W.F. van der Weg a , R. Rizzoli b,1 , C. Summonte b,1 , R. Pinghini b,1 , E. Centurioni b,1 , R. Galloni b,1 a Debye Institute, Utrecht UniÕersity, PO Box 80000, NL-3508 TA, Utrecht, The Netherlands b CNR-LAMEL, Via Gobetti 101, I-40129, Bologna, Italy Abstract Ž . We measured the temperature dependent current–voltage J – V characteristics of p a-SiC:Hrn c-Si heterojunction solar cells with different doping levels in the p a-SiC:H layer. For heterojunction solar cells with an undoped a-SiC:H layer, S-shaped J – V characteristics are observed at room temperature leading to poor factors. Below room temperature, such S-shape also appears for the cells with a highly doped p a-SiC:H layer. Detailed simulation studies showed that the origin of this S-shape lies in a reduced electric field in the c-Si depletion region, which, in combination with a hole accumulation at the interface, causes an increase in recombination losses. As long as the p a-SiC:H layer in these heterojunction cells is Ž 19 y3 . Ž highly doped G10 cm , these collection problems do not occur under standard operating conditions i.e., room 2 . temperature and 100 mWrcm illumination . q 1998 Elsevier Science B.V. All rights reserved. Keywords: Heterojunction solar cells; Photocarrier collection; Electric field; Recombination losses 1. Introduction Recent studies on amorphous-crystalline silicon heterojunctions have indicated the potential for these materials to be used as low cost, high efficient solar wx cells 1 . Despite this potential, the exact operation of these cells is not fully understood. In particular the electronic transport under illumination and the ef- fects of doping of the amorphous silicon window layer on the photocarrier collection are not under- wx stood. In previous work 2 we had already investi- gated the effects of temperature and illumination on Ž . the current–voltage J – V characteristics of doped ) Corresponding author. Tel.: q31-30 2532467; fax: q31-30 2543165; e-mail:cleef@fys.ruu.nl. 1 Tel.: q39-51 6399131; fax: q39-51 6399216. p q a-SiC:Hrn c-Si heterojunction cells. It was found that the band discontinuities at the a–c interface play a role in the collection of photogenerated carriers. In this work, we have studied by temperature dependent J – V measurements, the collection of photogenerated carriers in heterojunction cells with different doping levels in the p a-SiC:H layer. The correlation be- tween the experimental J – V characteristics and sim- ulations provides important information on the trans- port which takes place inside the device, in particular Ž . near the amorphousrcrystalline a–c interface. 2. Experimental Ž . Thin 10 to 30 nm boron doped p a-SiC:H layers were deposited by plasma enhanced chemical vapour 0022-3093r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0022-3093 98 00210-5