The tunnel oxide passivated contact (TOPCon) is a promising technology improving the efficiency of Si solar cells by cutting recombination losses and simplifying the solar cell design (1D junction design). The objective of this paper is to investigate possible contact materials having a high/low work function for passivated contacts thereby enabling the realization of a double-sided contact Si solar cell featuring n-type TOPCon on the front and p-type TOPCon at the rear side. The main part of this paper deals with the eligibility of thin atomic layer deposited (ALD) AZO (aluminum doped zinc oxide) interlayers sandwiched between n-TOPCon and ITO (tin doped indium oxide) in order to avoid sputter damage. It will be demonstrated that the insertion of ALD AZO improved the efficiency by 0.8% abs. and lead to a maximum efficiency of 20.2%. Finally, WOx and MoOx which have a high work function are identified as promising contact layers for p-TOPCon
In this investigation we compare intrinsic hydrogen diluted amorphous a-Si:H(i) layers deposited by inductively coupled plasma (ICP) to the standard parallel plate (PP) plasma, driven by 13.5 MHz power source. We analyze and compare the growth rate, optical energy gap, homogeneity, passivation quality, and most importantly silicon heterojunction solar cell performance. The ICP a-Si:H(i) layer shows superior properties regarding the growth rate, however, we obtain a slightly better passivation quality with the PP a-Si:H(i) layer, with Voc values up to 723 mV. Looking at the overall solar cell performance we were not able to see any difference between ICP and PP silicon heterojunction solar cell. The best solar cell (with an ICP a-Si:H(i) layer) has an efficiency of 18.7%
We present the first silicon solar cells processed at Fraunhofer ISE featuring an amorphous/crystalline silicon heterojunction rear emitter and a diffused front surface field.In this work, we focus on the optimization of the silicon heterojunction rear emitter of n-type silicon solar cells with regards to the intrinsic hydrogenated amorphous silicon a-Si:H(i) and boron-doped hydrogenated amorphous silicon a-Si:H(p) layer thickness and the influence of a transparent conducting oxide layer on the rear emitter surface. Efficiencies up to 19.1 % (V oc = 687 mV, J sc = 34.9 mA/cm 2 , FF = 79.9%) have been reached for non-textured solar cells on n-type absorbers. Furthermore, we attained an efficiency of 19.8% on textured p-type absorbers featuring an amorphous/crystalline silicon heterojunction rear emitter.
As a high-efficiency silicon solar cell concept amorphous silicon/crystalline silicon (a-Si:H(n,p)/c-Si (p,n)) hetero-junction solar cells are of great scientific interest [1, . The a-Si:H emitter is deposited by plasma-enhanced chemical vapor deposition (PECVD). The biggest challenge is to avoid recombination at the a-Si:H(i)/c-Si interface where the p-n junction is located. A clean, smooth, hydrogen terminated c-Si surface is supposed to be mandatory for a high passivation quality of the deposited layer [3, 4]. It is well established that treatment in dilute hydrofluoric acid (dHF) solution (1-10%) produces a hydrogen-terminated, clean Si surface [e.g. 5, 6, 7]. H-termination is supposed to rise with increasing etch time [8]. Whereas prolonged rinsing after the etch step leads to a formation of OH-groups at the surface [8]. Because of the high sensitivity of the a-Si:H(i)/c-Si interface the influence of prolonged etching in dHF (1%) as well as prolonged rinsing in deionized water (DI water) on the passivation quality of the deposited a-Si:H(i) layer has to be carefully studied. Also the possibility of decreased hydrophobicity and a possible iron recontamination from the HF has been taken into account.
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