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.