MATERIALS AND TECHNOLOGIES FOR FORMING TRANSPARENT- CONDUCING-OXIDE FOR SOLAR CELLS LI Xiang

Future development The materials The Technologies

Film deposition technologies DC/RF Magnetron Sputtering Pulsed Laser Deposition Reactive Environment Hollow Cathode Deposition Spray Pyrolysis Deposition Atomic Layer Deposition Reactive Sputtering Target or source Transfer agent Substrate

DC/RF MAGNETRON SPUTTERING (DCMS/RFMS) 1. Electro-magnetic field is used to excite and ionize target species; 2. Uneven erosion of target material; 3. Most widely used deposition technique; 4. Expensive in terms of ceramic target material preparation. 5. Low process temperature. The pressure is 4 × 10 −4 Pa. The target is a mixture of ZnO (99.99% purity) and Al2O3 (99.99% purity). In the end, a low resistivity of 4.62 × 10 −4 Ω cm and average optical transmission of 93.7% is achieved at a sputtering power of 300W, with Ar air flow of 30sccm and target distance of 7cm

PULSED LASER DEPOSITION (PLD) 1. Excellent approach to study TCO film without knowing the chemical or crystal property of target material; 2. Precise shot-to-shot control of deposition process; 3. Stoichiometric transfer of materials, minimum waste of materials; 4. multilayer/multicompound TCO film deposition.

REACTIVE ENVIRONMENT HOLLOW CATHODE DEPOSITION (REHCD) 1.Hollow cathode configuration; 2.prevent reactive gas from reaching the target; 3.maintaining steady, high deposition rate. 4.*Different from Reactive Sputtering.

SPRAY PYROLYSIS DEPOSITION (SPD) 1. Temperature on the surface of the substrate; 2. Precursor solution composition and density; 3. Effectiveness of atomization of Precursor solution; 4. Aerosol transportation/spray 5. Decomposition of precursor

Binary Compound: ZnO, SnO2, In2O 3 Ternary compounds: Cd2SnO4, CdSnO 3 CdIn2O binary-binary compound systems ternary-ternary compound systems Materials

FUTURE RESEARCH DIRECTIONS IN TCO FILMS 1.1/ρ = Nµe, the conflict between transparency and resistivity. N ↑, 1/ ρ ↑, transparency ↓; N ↓, 1/ ρ ↓, transparency ↑; 2.Increase µ, electron mobility; 3.More research should be done on how deposition process can influence electron mobility instead of increasing dopant concentration.

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