High Efficiency (>17%) Si‐Organic Hybrid Solar Cells by Simultaneous Structural, Electrical, and Interfacial Engineering via Low‐Temperature Processes

Abstract

Highly efficient organic–inorganic hybrid solar cells of Si‐poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) have been demonstrated by simultaneous structural, electrical, and interfacial engineering with low processing temperature. Si substrate has been sculpted into hierarchical structure to reduce light reflection loss and increase interfacial junction area at the same time. Regarding the electrical optimization, highly conductive organic PEDOT:PSS layer has been formulated with low sheet resistance. It is argued that the sheet resistance, rather than conductivity, is the primary parameter for the high efficiency hybrid cells, which leads to the optimization of thickness, i.e., thick enough to have low sheet resistance but transparent enough to pass the incident sunlight. Finally, siloxane oligomers have been inserted into top/bottom interfaces by contact‐printing at room ambient, which suppresses carrier recombination at interfaces and reduces contact resistance at bottom electrode. Contrary to high‐temperature doping (for the formation of front surface or back surface fields), wet solution processes or vacuum‐based deposition, the contact‐printing can be done at room ambient to reduce carrier recombination at the interfaces. The high efficiency obtained with low processing temperature can make this type of cells be a possible candidate for post‐Si photovoltaics.

Recent Advances of Synthesis, Properties, Film Fabrication Methods, Modifications of Poly(3,4‐ethylenedioxythiophene), and Applications in Solution‐Processed Photovoltaics

“…PEDOT:PSS film plays dual roles: 1) as top transparent electrode; 2) as hole-selective contact for n-type crystalline silicon to form a p + -n heterojunction (Figure 19d). The hybrid cells have currently achieved PCEs of over 17%, [308] getting close to a predicated value of over 21%. Optimizing PEDOT:PSS to improve its conductivity and reduce surface carrier recombination at the Si/PEDOT:PSS heterointerface is an efficient way to improve device performance.…”

Buffer-Free Inverted Photovoltaic Cells with Hybrid C60 /CuI Heterojunction

“…Compared to the normal devices, the inverted ones demonstrate substantially higher fill‐factor FF of 50% under illumination – Table . This can be attributed to a better physical contact between CuI and the fullerene due to suppression of charge carrier recombination when an inorganic layer is deposited on the organic one. Besides, the structure of the CuI layer deposited over C 60 is somewhat different from that being the case when the CuI layer is beneath C 60 (Figure S2, Supporting Information).…”

“…Hybrid photovoltaic cells are expected to combine the advanced concepts, realized in the still unstable organic‐based devices, with the reliable technologies and reproducibility of effects of the inherently stable inorganic semiconductors . Not surprisingly, the most demonstrative examples are associated with the concept of a bulk heterojunction, in which organic semiconductors, the donor, and acceptor materials, are blended using the solution techniques.…”

Ambipolar Passivated Back Surface Field Layer for Silicon Photovoltaics

“…[6][7][8] In light-emitting devices, free charges trapped in the defect states cause nonradiative recombination and hinder the charge transport, thereby lowering the photoluminescence quantum yield. [9][10][11] yielded PCEs up to ≈17% [40][41][42][43][44] In addition, additional doping processes or high-temperature vacuum processes involving the deposition of a-Si:H on the rear-side of Si are usually adopted to enhance the cell performance. [41,43,[45][46][47] D. Zielke et al [47][48][49] suggested "BackPEDOT" concept, in which PEDOT:PSS is spin-coated on the backside of the Si substrate.…”