Enable Pyrite as a High Performance Solar Material Using Photoelectrochemical and Transport Studies of Pyrite Single Crystals

摘要

The scale of the energy challenges demands earth-abundant and inexpensive solar materials that are made by less energy-intensive and costly processes. Iron pyrite (FeS2) is an earth-abundant semiconductor that has generated renewed interest due to its promising properties for solar energy conversion (band gap of 0.95 eV, high absorption coefficient, and high carrier mobility). However, the best solar conversion efficiency shown for single crystal pyrite has remained low (< 3%) limited by a low open circuit voltage (<200mV) and nanostructure pyrite has not shown any efficiency despite intense recent efforts. To understand the fundamental bulk and surface defects intrinsic to pyrite semiconductor, we performed systematic photoelectrochemical studies on pyrite single crystals and electrical transport (temperature dependent Hall effect and field-effect) studies using single crystal pyrite nanorods and nanoplates as study platforms. The combined electrochemical impedance spectroscopy and transport studies suggest the heavily doped p-type conduction behaviors observed for intrinsic n-type pyrite originates from strong Fermi level pinning due to surface defects. Such understanding allows us to develop strategies to mitigate these issues in order to improve the performance and eventually fulfill pyrite’s promise as a solar material.