Back-contacted Heterojunction Solar Cells Research Articles

Interfacial Band Engineering of Highly Efficient PEDOT:PSS/p‐Si/ZnO Heterojunction Solar Cells

Hybrid heterojunction solar cells (HHSCs) using different active materials as hole‐selective transport layers and electron‐selective transport layers show great potential in both low cost and high power conversion efficiency (PCE). Herein, PEDOT:PSS/p‐Si/ZnO backcontact heterojunction solar cells are prepared using the simple low‐temperature solution method. PEDOT:PSS is introduced into p‐Si‐based solar cells as an antireflective and passivation layer to optimize device performance. The effect of the work function (WF) of ZnO on device performance is investigated, and a PCE of 10.74% is achieved using low‐WF ZnO. In addition, the PEDOT:PSS layer is doped with Nafion, and the surface passivation quality of the p‐Si is dramatically enhanced. By optimizing the doping concentration of Nafion, the PCE of the optimized device reaches 11.43%, which is currently the highest PCE for p‐Si‐based solar cells using solution method. The findings provide a simple and promising method to achieve high‐performance PEDOT:PSS/p‐Si/ZnO HHSCs.

Back Contact Heterojunction Solar Cells Patterned by Laser Ablation

Back contact heterojunction (IBC-HIT) solar cells is one of the most promising technology for the upcoming generations of high efficiency crystalline-Silicon (c-Si) based photovoltaic modules [1]. However, the industrialization of the IBC-HIT technology is actually constrained by the complexity of the back side cell processing, which usually involves costly and time consuming photolithography steps. CEA-INES is currently developing a method based only on laser ablation for the structuration of IBC-HIT solar cells [2]. Laser ablation is indeed a fast and low cost technique that also allows the patterning of the back side amorphous (a-Si:H) layers on large area IBC-HIT solar cells. However laser irradiation might induce some damage at the c-Si/a-Si:H interface thus limiting the final performance of the devices. In this work, we compare the results obtained with our laser patterning process for different stack configurations and laser ablation conditions (532nm and 355nm). We will also discuss about the criteria used for the choice of the different materials and the laser ablation conditions needed in order to successfully pattern both the emitter and BSF (Back Surface Field) regions of the cell. Our best cell efficiency achieved up to now is 20.55% on an area of 18.11 cm2.

(Invited) Three-Dimensionally Structured Thin Film Heterojunction Photovoltaics on Interdigitated Back-Contacts

Fabrication and properties of three-dimensionally structured back-contact heterojunction solar cells are described. A variety of devices are explored, all of which were fabricated by electrochemical deposition of a semiconducting material on one of two interdigitated electrodes in a comb structure followed by deposition of a second semiconducting material over the entire surface, including over both the bare and coated electrodes in the comb. The performance of fabricated devices is described and interpreted using a simplified model of the device geometry, light absorption and carrier transport. The results demonstrate that the processes and structures are amenable to a broad array of materials and deposition techniques, providing well-defined geometries amenable to fabrication and study of 3-D structured photovoltaic devices.

Planar rear emitter back contact silicon heterojunction solar cells

A planar rear emitter back contact silicon heterojunction (PreBC-SHJ) solar cell design is presented, which combines the advantages of different high efficiency concepts using point contacts, back contacts, and silicon heterojunctions. Electrically insulated point or stripe contacts to the solar cell absorber are embedded within a planar hydrogenated amorphous silicon emitter layer deposited at low temperature on the rear side. The new solar cell design requires less structuring and allows large structure sizes, enabling the use of low-cost patterning technologies such as inkjet printing or screen printing. By means of numerical computer simulation the efficiency potential of back contacted heterojunction solar cells is shown to exceed 24%. First PreBC-SHJ solar cells have been realized and exhibit higher short circuit currents than our state-of-the-art front contacted silicon heterojunction reference solar cells.