Conduction Band Energy‐Level Engineering for Improving Open‐Circuit Voltage in Antimony Selenide Nanorod Array Solar Cells

Abstract

Antimony selenide (Sb2Se3) nanorod arrays along the [001] orientation are known to transfer photogenerated carriers rapidly due to the strongly anisotropic one‐dimensional crystal structure. With advanced light‐trapping structures, the Sb2Se3 nanorod array‐based solar cells have excellent broad spectral response properties, and higher short‐circuit current density than the conventional planar structured thin film solar cells. However, the interface engineering for the Sb2Se3 nanorod array‐based solar cell is more crucial to increase the performance, because it is challenging to coat a compact buffer layer with perfect coverage to form a uniform heterojunction interface due to its large surface area and length–diameter ratio. In this work, an intermeshing In2S3 nanosheet‐CdS composite as the buffer layer, compactly coating on the Sb2Se3 nanorod surface is constructed. The application of In2S3‐CdS composite buffers build a gradient conduction band energy configuration in the Sb2Se3/buffer heterojunction interface, which reduces the interface recombination and enhances the transfer and collection of photogenerated electrons. The energy‐level regulation minimizes the open‐circuit voltage deficit at the interfaces of buffer/Sb2Se3 and buffer/ZnO layers in the Sb2Se3 solar cells. Consequently, the Sb2Se3 nanorod array solar cell based on In2S3‐CdS composite buffers achieves an efficiency of as high as 9.19% with a VOC of 461 mV.

Enhanced Efficiency and Stability in Sb2S3 Seed Layer Buffered Sb2Se3 Solar Cells

“…[8,9] Moreover, Sb 2 Se 3 is very attractive in PV thanks to the abundance and less toxicity of Sb, S, and Se elements. [10][11][12] The quasi-1D crystalline structure of orthorhombic Sb 2 Se 3 , i.e., ribbon-like (Sb 4 Se 6 ) n units bonded by weak van der Waals (vdW) forces along [100] and [010] direction, provides unique photogenerated carrier transport behavior along with the ribbons and self-passivate the grain boundaries. [10,13,14] For high carrier mobility, the ribbons grew along [00l] direction is the most preferred orientation proved by theoretical calculation and experimental results since the ribbons are stacked by only vdW attraction and free from dangling bonds.…”

Crystal Growth Promotion and Defects Healing Enable Minimum Open‐Circuit Voltage Deficit in Antimony Selenide Solar Cells

“…Herein, the recombination mechanism referred to where and how the recombination occurred was systematically investigated. First, temperature-dependent open-circuit voltage (V OC -T) measurement was carried out to obtain the activation energy (E a ), according to the following equation [43]…”

“…Herein, the recombination mechanism referred to where and how the recombination occurred was systematically investigated. First, temperature‐dependent open‐circuit voltage ( V OC ‐ T ) measurement was carried out to obtain the activation energy ( E a ), according to the following equation [ 43 ] Hence, E a value could be calculated by extrapolating the V OC to y ‐axis ( T = 0 K). In principle, the E a of interface recombination is lower than E g , and E a of SCR recombination is equal to E g .…”

Interface Modification Uncovers the Potential Application of SnO2/TiO2 Double Electron Transport Layer in Efficient Cadmium‐Free Sb2Se3 Devices

“…Currently, although the champion efficiency of Sb 2 Se 3 TFSC is 9.2%, a pure CdS or Cd doped thin film is prevalently adopted as the electron transport layer (ETL) or buffer layer for most of the efficient Sb 2 Se 3 TFSC with superstrate or substrate configuration. [9][10][14][15][16][17][18][19] Considering the short circuit current density (J sc ) of Sb 2 Se 3 TFSC will be limited by the parasitic absorption of CdS layer (2.4 eV) in wavelength below 520 nm, and the green environmental demands today, avoiding or reducing the usage of cadmium element remains an important issue for the future development of Sb 2 Se 3 technology. Thus, searching for the proper Cd-free ETL is very important.…”