TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: The solar cell further comprises an antireflective coating layer disposed on another portion of the negative-type region. In the solar cell: the crystalline calcium oxide is present in at 1-6 wt.%; and the aluminum is present at 94-99 wt.%. The positive-type silicon substrate is at least one of a polycrystalline substrate or a single crystalline substrate. Preferred Process: The step (a) comprises screen printing the aluminum paste composition on the back-side of the positive-type silicon substrate. The steps (c) and (d) are done at the same time.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The aluminum paste further comprises an optional additive comprising glass frits, amorphous silicon dioxide, organometallic compounds, boron nitride, and/or metal salts. Preferred Components: The crystalline calcium oxide is present at 0.05-8 wt.% of the composition. The aluminum powder: is present at 45-80 wt.% of the composition; and comprises nodular aluminum, spherical aluminum, flake aluminum, and/or irregularly-shaped aluminum. The glass frit is present at 0.01-5 wt.%. The aluminum back electrode further comprises 0.1-10 wt.% of an optional additive, comprising silicon dioxide, boron nitride, and/or metal oxides. EXAMPLE - Air-atomized nodular aluminum powder (80 wt.%) and organic vehicle 1 (OV1) (comprised of 43.5% terpineol solvent, 43.5% dibutyl carbitol, 7.5% oleic acid, and 5.5% ethyl cellulose) (20 wt.%) were mixed to obtain a pre-wet aluminum slurry. The pre-wet aluminum slurry (247.9 g) was mixed with organic vehicle 2 (OV2) (comprised of 46.7% terpineol solvent, 40.9% dibutyl carbitol, and 12.4% ethyl cellulose) (6.7 g), epoxidized octyl tallate (1.3 g), polyunsaturated oleic acid (0.8 g), and a mixture of wax and hydrogenated castor oil (2.7 g) to obtain a pre-paste mixture. The pre-paste mixture was further mixed using a planetary centrifugal mixer for 30 seconds at 2000 rpm. The mixing process was repeated for two more times to ensure uniform mixing to form a pre-paste. The pre-paste was then dispersed using a high shear mixer at 1800 rpm to 2200 rpm for 3 minutes. The pre-paste was also stirred by hand to eliminate possible unmixed areas at the side to obtain a first batch of pre-paste. A second batch of similar quantity pre-paste was prepared with the same steps and two batches were combined together. To this, organic vehicle 3 (OV3) (a 50/50 blend of terpineol solvent and dibutyl carbitol) (18.01 g) was added and mixed to obtain master batch paste A. The master batch paste A (45.5 g), OV2 (1.06 g), OV3 (0.118 g), and calcium oxide (3.32 g) were mixed using high shear mixer at 1800-2200 rpm for 3 minutes to obtain the aluminum paste composition.