Engineering topics

Russell, Thomas

Publications and source records attributed to Russell, Thomas.

3 records

DOE OSTI2020

Unraveling the Crystallization Kinetics of 2D Perovskites with Sandwich-Type Structure for High-Performance Photovoltaics

2D perovskite solar cells with high stability and high efficiency have attracted significant attention. A systematical static and dynamic structure investigation is carried out to show the details of 2D morphology evolution. A dual additive approach is used, where the synergy between an alkali metal cation and a polar solvent leads to high-quality 2D perovskite films with sandwich-type structures and vertical phase segregation. Such novel structure can induce high-quality 2D slab growth and reduce internal and surface defects, resulting in a high device efficiency of 16.48% with enhanced continuous illumination stability and improved moisture (55-60%) and thermal (85°C) tolerances. Transient absorption spectra reveal the carrier migration from low n to high n species with different kinetics. An [PbI 6 ] 4- octagon coalescence transformation mechanism coupled with metal and organic cations wrapped is proposed. By solvent vapor annealing, a recrystallization and reorientation of the 2D perovskite slabs occurs to form an ideal structure with improved device performance and stability.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Fabrication processes for effectively transparent contacts

In conventional solar cells with metal contacts, a non-negligible fraction of the incoming solar power is immediately lost either through absorption or reflection upon interaction with the contacts. Effectively transparent contacts (“ETCs”) for solar cells can be referred to as three-dimensional contacts designed to redirect incoming light onto a photoabsorbing surface of a solar cell. In many embodiments, the ETCs have triangular cross-sections. Such ETCs can be placed on a photoabsorbing surface such that at least one of their sides forms an angle with the photoabsorbing surface. In this configuration, the ETCs can redirect incident light onto the photoabsorbing surface, mitigating or eliminating reflection loss compared to conventional solar cells. When constructed in accordance with a number of embodiments of the invention, ETCs can be effectively transparent and highly conductive.

14 SOLAR ENERGY↗

DOE OSTI2020

Bimolecular crystal instability and morphology of bulk heterojunction blends in organic and perovskite solar cells

The performance of polymer:fullerene bulk heterojunction (BHJ) solar cells is significantly influenced by the morphology of electron donor and acceptor blends under the premise that electronic structure is complimentary regarding donor and acceptor materials. There are many cases where intimate mixing of donor and acceptor perturbs the electronic structure, which fundamentally changes the transport and photovoltaic characteristics. In this work, we present the bimolecular crystal packing of polymers and fullerenes, and investigate the correlation between device performance and structural details. We find that bimolecular crystallization can reorganize polymer chain packing, leading to poor electron transport and device performance. The size compatibility and the passivation of entropy penalty led to cocrystallization instability, which was clearly seen by in situ GIWAXS data. PC 61 BM is found to intercalate into side chains of PQT by reorganizing both PQT and PC 61 BM, forming stable, highly ordered bimolecular crystals. The poor electron transport in bimolecular crystal domain could account for the poor device performance in both perovskite and organic solar cells. Bis-PC 61 BM, on the other hand, only forms loosely packed aggregates in solution, and then rapidly phase separated into large domains with an edge-on interfacial orientation and performed poorly in solar cells.

36 MATERIALS SCIENCE↗