Grant: $100,000 - National Science Foundation - Jul. 1, 2009
50% voted satisfied - 50% voted not satisfied - 2 vote(s) cast
Award Description: Solarity is a start-up company located in the Innovation Park at Penn State that is focusing on manufacturable ways to make solar cells more efficient and less expensive. We have patented a novel architecture for solar cells which employs lateral collection of photo-generated charge carriers. The design is an improvement over existing planar architectures because it allows for greater utilization of sunlight and active layer materials. One of the major drawbacks of most solar cell configurations is that they collect charge carriers (electrons and holes) at their top and bottom surfaces. This configuration limits the thickness of the light absorbing layer to be approximately the same as the collection length of the charge carriers. Solarity?s lateral collection solar cells circumvent any thickness limitations by decoupling the directions of light absorption and charge carrier collection. Specifically, charge carriers are collected laterally (perpendicular to the direction of light absorption) by columnar electrodes that extend into the active layer of the device. The height and spacing of the columns can be varied in order to match the light absorption and charge transport properties of the active layer material. This project aims to develop procedures for constructing columnar lateral collection electrodes which match the material properties of amorphous silicon (a-Si:H), which is a popular low-cost light absorber. Importantly, the absorption and collection lengths of a-Si:H are quite short ? tens to hundreds of nanometers ? so the collecting electrodes must be nano-scale as well. A short absorption length means that light is absorbed very well; so a-Si:H is a good choice for solar cell applications. However, it is not a great conductor of photo-generated charge carriers. Lateral collection helps to remedy this mismatch.
Project Description: The technical objectives to be accomplished during the proposed Phase 1 research are concentrated on fully developing and evaluating the use of nano-structured electrodes in solar cells based on inexpensive absorber materials (e.g., a-Si:H). The electrode structure was designed to enhance the photo-generated carrier collection of lateral collection solar cell devices and the optimization of the electrode fabrication process is very important to achieve the ultimate goal of the project. PS-b-PMMA diblock copolymer films were used to define the nano-scale electrode patterns. After processing, the poly(methyl methacrylate) (PMMA) and polystyrene (PS) phase-separated into nanoscale features. The PMMA phase formed well-ordered, vertically oriented cylinders arranged in a hexagonal pattern. The PS formed a matrix which surrounded the PMMA cylinders. The PMMA cylinders were 50 nm in diameter and 50 nm apart (edge to edge distance between the cylinders). Using the resulting nano-scale templates, three materials were explored as the electrode materials: aluminum-doped zinc oxide (AZO), doped amorphous silicon (a-Si:H), and PEDOT (a conductive polymer). The materials were selected based on their potential energy levels, which are positioned favorably relative to those of the light absorbing materials (e.g., intrinsic a-Si:H, P3HT:PCBM). Procedures were developed and optimized to deposit each of the above electrode materials into the nano-scale templates. The final dimensions of the nano-scale electrode structures for the three materials were 55 nm in diameter, 40 nm in spacing, and 200 nm in height. For the doped a-Si:H, 400 nm high electrode structures were also fabricated. Additionally, single junction a-Si:H devices were fabricated to validate the device fabrication processes downstream of the nano-scale electrode formation step. These control devices were fabricated on 10 nm thick AZO-coated ITO electrodes and afforded a power conversion efficiency (PCE) of 3.9%.
Jobs Summary: N/A (Total jobs reported: 0)
Project Status: More than 50% Completed
This award's data was last updated on Jul. 1, 2009. Help expand these official descriptions using the wiki below.
Funds from this award have been disbursed to sub-grantees. Click here to see a list of sub-grantees.