Scanning photocurrent microscopy to investigate materials for photovoltaics

As the world becomes even more dependent on energy there is a dire need to find a clean and renewable energy source. Solar energy has the possibility to provide more then enough clean energy the world needs, yet, it is still not an option available to many due to production cost. New cheaper materials are investigated in hopes of building a low cost and efficient photovoltaic (PV). One method that can dramatically lower the cost of production is to use materials that can be deposited from solutions. Although many candidates fit the requirements needed to be solution processable, this technique consistently makes PVs with much lower efficiencies then their crystalline counter parts. Information about charge transfer and extraction processes of the charge carriers are necessary to optimize them. Scanning photocurrent microscopy (SPCM) is a technique that scans a sample across a focused laser beam and collects photocurrent as a function of position. Photoluminescence and reflectance are collected simultaneously providing information about the morphology and recombination. Information gathered from SPCM gives insight to intrinsic recombination and transport properties of the material. This dissertation will look at multiple systems used in PVs. First the space charge regions of a Langevin polymer with and without an additive are compared to see the effects of morphology on collection. A Langevin polymer is then compared to a non-Langevin to find intrinsic differences between them. A perovskite solar is scanned using different polarized light. Finally, A new thin film and new device architecture was probed using SPCM.