Efficient, Low-Cost Organic-Inorganic Hybrid Solar Cells via Materials, Interface, and Device Structure Design

The concept of the inter-mixing of donor-acceptor materials in a single layer revolutionized the solar cell technology. The commonly used materials are lack of strong absorption in the near-infrared region. Pyrite FeS 2 is a promising material because of its high absorption in the range of 300--1100 nm. In addition, it is abundant, non-toxic and has long term stability as well as the extraordinary electrical properties. Pyrite FeS2 hierarchical microparticles consisting of cubic crystals with defined {100} faceted textures were synthesized using a hydrothermal method with the presence of ethylenediamine and polyvinylpyrrolidone. Short, branched, and chromosome-like pyrite FeS2 rods with a diameter of 10 nm and a length of 20--30 nm as well as quasi-cubic NC agglomerates with a size of 200 nm were obtained by hot injection methods. The growth of anisotropic iron pyrite nanocrystals (NCs) follows the oriented attachment mechanism at the early growth stage of the hot injection synthesis followed by Ostwald ripening mechanism as time progresses.;In the fabrication of inverted organic-inorganic hybrid solar cells with pyrite NCs, we realize an effective hole transport layer (HTL) improves the performance of the solar cells and provides additional protection against water and oxygen. The HTL serves as a selective contact by extracting holes while concurrently blocking electrons, thereby reducing dark (leakage) current and enhancing the open circuit voltage (VOC), short circuit current (JSC), and fill factor (FF). The inverted hybrid CdSe -polymer solar cells with the poly (3, 4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS)/MoO3 dual HTLs showed superior performance over those with a single HTL of PEDOT:PSS or MoO3. The enhancement in electron transport in the active layer, the improvement in hole extraction at active layer/anode interface as well as a prevention of leakage current account for the enhancement in the efficiency of the solar cells with dual HTLs.;In order to achieve an efficient charge separation and correlates the film morphology and grain size with the device performance. A two-step solution process with thermal plus solvent vapor-assisted thermal annealing was developed for the fabrication of binary Pb-Sn triiodine perovskite films. This was an effective method to make films with large and smooth grains. Using this new process to control and manipulate film morphology, grain size, and especially the distribution of metal cations in binary metal perovskite layers, opens an avenue to grow perovskite materials with desired properties to enhance device performance.