Designing and Probing Photovoltaic and Photocatalytic Materials

Meeting Program — November 2012

Jason B. Bax­ter
Depart­ment of Chem­i­cal and Bio­log­i­cal Engi­neer­ing
Drex­el Uni­ver­si­ty
Philadel­phia, PA

Abstract — The sun­light inci­dent on the earth pro­vides 10,000 times more pow­er than is need­ed to meet glob­al demand. How­ev­er, con­vert­ing this ener­gy into elec­tric­i­ty or fuels effi­cient­ly and cost effec­tive­ly remains a great chal­lenge. Nanos­truc­tured solar cells present oppor­tu­ni­ties to inex­pen­sive­ly con­vert sun­light to elec­tric­i­ty through the use of archi­tec­tures tai­lored on the nanome­ter to microm­e­ter length scale. Pla­nar solar cells are sub­ject to oppos­ing con­straints where thick films are required for light absorp­tion while thin­ner films are desir­able for effi­cient charge sep­a­ra­tion. Extreme­ly thin absorber (ETA) solar cells can decou­ple these con­straints by using a thin absorber at the inter­face between high­ly struc­tured p- and n-type lay­ers. In this talk, I will describe our work on ETA solar cells that use a thin CdSe coat­ing on a ZnO nanowire array to absorb light and inject elec­trons into the oxide. Ratio­nal design of these archi­tec­tures requires con­trol over mor­phol­o­gy and microstruc­ture of the mate­ri­als, as well as knowl­edge of mate­r­i­al prop­er­ties such as pho­toex­cit­ed car­ri­er life­times and mobil­i­ties. Our approach uti­lizes a com­bi­na­tion of solar cell mea­sure­ments and ultra­fast tran­sient absorp­tion spec­troscopy to under­stand the effects of CdSe thick­ness, anneal­ing con­di­tions, and inter­fa­cial treat­ments on the dynam­ics and effi­cien­cy of charge car­ri­er sep­a­ra­tion, and ulti­mate­ly on the solar-to-elec­tric ener­gy con­ver­sion effi­cien­cy. These stud­ies pro­vide guide­lines for archi­tec­ture design and mate­ri­als selec­tion for ETA solar cells.

Jason B. Baxter

Jason B. Bax­ter

Biog­ra­phy — Dr. Jason B. Bax­ter is an Assis­tant Pro­fes­sor in the Depart­ment of Chem­i­cal and Bio­log­i­cal Engi­neer­ing at Drex­el Uni­ver­si­ty in Philadel­phia, PA, where he began in 2007. He received his B.Ch.E. from the Uni­ver­si­ty of Delaware in 2000, where he did under­grad­u­ate research on dye sen­si­tized solar cells at the Insti­tute of Ener­gy Con­ver­sion under the guid­ance of Prof. T.W. Fras­er Rus­sell. He earned his Ph.D. in chem­i­cal engi­neer­ing from the Uni­ver­si­ty of Cal­i­for­nia San­ta Bar­bara in 2005. Advised by Prof. Eray S. Aydil and fund­ed by an NSF Grad­u­ate Research Fel­low­ship, he inves­ti­gat­ed growth and char­ac­ter­i­za­tion of ZnO nanowires and their appli­ca­tion in dye sen­si­tized solar cells. From 2005–2007, Dr. Bax­ter was an ACS Petro­le­um Research Fund Alter­na­tive Ener­gy Post­doc­tor­al Fel­low at Yale Uni­ver­si­ty. There he worked with Prof. Charles A. Schmut­ten­maer in the Chem­istry Depart­ment on the appli­ca­tion of time-resolved ter­a­hertz spec­troscopy to probe tran­sient pho­to­con­duc­tiv­i­ty in oxide thin films, nanopar­ti­cles, nanowires, and bulk crys­tals.

Dr. Baxter’s cur­rent research inter­ests are in design­ing, fab­ri­cat­ing, and prob­ing semi­con­duc­tor nano­ma­te­ri­als and thin films for solar ener­gy con­ver­sion. Most cur­rent efforts focus on solar-to-elec­tric ener­gy con­ver­sion, but the group has grow­ing inter­est in pho­to­cat­alyt­ic water split­ting for clean and renew­able hydro­gen pro­duc­tion. Var­i­ous projects in the group include extreme­ly thin absorber solar cells, organ­ic solar cells, microre­ac­tor depo­si­tion of grad­ed thin films for high-through­put char­ac­ter­i­za­tion, and ultra­fast pump-probe spec­troscopy to mea­sure charge car­ri­er dynam­ics. The gen­er­al focus of the group is on striv­ing to under­stand how mate­ri­als and inter­faces affect device per­for­mance, and how these mate­ri­als and inter­faces can be con­trolled dur­ing the fab­ri­ca­tion process. Low-tem­per­a­ture solu­tion pro­cess­ing meth­ods are used when­ev­er pos­si­ble to pro­vide a path­way to low-cost, scal­able man­u­fac­tur­ing.
Dr. Bax­ter advis­es a group of 4 PhD stu­dents, 2 MS stu­dents, and 8 BS stu­dents. He has pub­lished near­ly 25 papers, which have col­lec­tive­ly gar­nered well over 1000 cita­tions. He has been award­ed over $1 mil­lion in fund­ing as lead inves­ti­ga­tor and anoth­er $3 mil­lion as co-inves­ti­ga­tor. He received the NSF CAREER Award in 2009.