Enhanced Selective Contact Behavior in a-Si:H/oxide Transparent Photovoltaic Devices via Dipole Layer Integration

Transparent photovoltaic (TPV) devices have the potential to revolutionize photovoltaic (PV) technology by enabling on-site generation while minimizing visual impact. However, a major challenge in the development of TPV, as well as for many PV technologies, is the open-circuit voltage (V_oc) deficit, which limits their efficiency. In this work, the development of wide-bandgap inorganic-based TPV devices is reported with a focus on low-cost, earth-abundant, stable, and nontoxic materials. The device structure consists of an ultrathin hydrogenated amorphous silicon (a-Si:H) absorber and metal-oxide layers as selective contacts. Herein, novel approach is presented to significantly improve device performance, especially in V_oc, by introducing molecular dipoles in the device electron-transport layer. By incorporating polyethyleneimine or poly(amidoamine) G₁ and G₂ dipoles, V_oc (from 410 mV up to 638 mV) is significantly increased without sacrificing the average photopic transmittance of the device, leading to a record efficiency for this particular approach in TPV. Measurements confirm excellent long-term stability. This approach can potentially allow tuning the work function of the selective contacts enabling the use of low-cost, earth-abundant materials that are not optimized for a particular absorber. Furthermore, this solution circumvents the issue of low V_oc by a simple interface treatment.