Trouble with Transistor Switch (2n3906)
There are a number of problems here:

1N4148 is not a Schottky diode, and certainly can't handle 5 A.

If the panel puts out 6 V max, then it's not going to charge the 9 V battery unless it is very low.

You are overdriving the LEDs at full battery voltage.  You say the LEDs drop 3.3 V each.  Figure 200 mV for the transistor when fully on, so that leaves 2.2 V across each of R4, R5, and R6, which results in 22 mA.

The turn on/off of the transistor will be "soft".  Perhaps this is what you want, but something with a little hysteresis will cause the LEDs to snap on and off.